Integrated circuits (ICs) often vary in power consumption and performance with a change in a process and/or temperature. A process region or a process corner may refer to variations in fabrication process that may cause transistor (or device) operation or device speed to vary. For example, in a slow device (or slow corner or worst case corner), the speed of the device is relatively slow (e.g., the amount of time required for the device to charge, discharge or change states may be longer) due to a lower drain current for a given gate voltage. Similarly, in a fast device (or a fast corner or best case corner), the speed of the device is relatively fast due to a higher drain current for the same gate voltage. For example, a fast device may have a lower threshold voltage, which may allow the device (or transistor) to turn on (or switch states) at a lower gate voltage and/or may produce a higher drain current at the same gate voltage. For example, a device having a higher drain current for a specific gate voltage may charge and discharge (and therefore, switch states) faster than a device that has a lower drain current for the same gate voltage.
In many cases, ICs are usually designed for the worst case (or slow) process corner. A power supply voltage or VDD is typically selected and supplied to the IC based on the worst case or slow process corner. The supply voltage that is selected for a worst case or slow process corner is higher than the supply voltage that is necessary for a best case or fast process corner device to operate properly, and may result in excessive power consumption by the fast process corner device.